Air intake duct

ABSTRACT

There is provided an air intake duct capable of fully achieving intake-air noise attenuation effect. The air intake duct has a duct wall section formed of resin in form of tube and configured to introduce external air into an internal combustion engine or alternate power supply system. The duct wall section is provided with a silencing member formed of a lamination of a surface layer formed of a non-woven fabric to which thermosetting resin is impregnated and a ventilation adjusting layer formed of an extendable paper material having a surface in which a plurality of concave and convex portions are formed, and the silencing member includes at least one pair of the surface layers on front and back surfaces of at least one pair of the ventilation adjusting layers, and an intermediate layer is formed between the paired ventilation adjusting layers, the intermediate layer being formed of a same material as that of the surface layer.

TECHNICAL FIELD

The present invention relates to an intake duct, and more specifically,an air intake duct capable of reducing intake noise generated at a timeof introducing outside air into an internal combustion engine oralternative power system or engine.

BACKGROUND TECHNOLOGY

Conventionally, there are known a technology of adoption of varioustypes of air intake ducts for reducing intake noise in addition toreduction of noise of specific frequency calculated based on resonancetheory by Helmholtz by locating a resonator in an intake passage forreducing intake noise generated in an intake system at a time ofintroduction of external air into an internal combustion engine such asgasoline engine or alternative power mechanism such as fuel cell orbattery.

An intake duct disclosed in Patent Document 1 is formed with a duct wallformed of resin into tubular shape, and in the intake duct forintroducing external air into an internal combustion engine, the ductwall is provided with a waterproof/moisture-permeable (merely permeable)member formed by laminating a water repellent layer having high densityfiber and a waterproof/permeable layer formed of microporous membrane.

The thus formed intake duct disclosed in the Patent Document 1 isprovided with the waterproof/permeable layer for the duct wall of thetubular intake duct, so that moisture invading into the engine room canbe prevented from entering the intake duct. In addition, intake noisecan be reduced by noise absorption function of the microporous membrane.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent Laid-open Publication No. 2009-293442

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, the structure of the conventional intake duct described aboveis effected with waterproof treatment, intake noise reduction effectcannot be sufficiently achieved, and hence, originally requiredsilencing function for a silencing duct cannot be also sufficientlyachieved, being inconvenient.

Means for Solving the Problem

The air intake duct according to the present invention has a duct wallsection formed of resin in form of tube and configured to introduceexternal air into an internal combustion engine or alternate powersupply system, wherein the duct wall section is provided with asilencing member formed of a lamination of a surface layer formed of anon-woven fabric to which thermosetting resin is impregnated and aventilation adjusting layer formed of an extendable paper materialhaving a surface in which a plurality of concave and convex portions areformed, the silencing member comprises at least one pair of the surfacelayers on front and back surfaces of at least one pair of theventilation adjusting layers, and an intermediate layer is formedbetween the paired ventilation adjusting layers, the intermediate layerbeing formed of a same material as that of the surface layer.

It may be preferred that, in the air intake duct of the presentinvention, the intermediate layer is bonded to the ventilation adjustinglayers by means of bonding agent.

It may be preferred that, in the air intake duct of the presentinvention, the silencing member has a thickness of 1.0 to 3.0 mm.

It may be preferred that, in the air intake duct of the presentinvention, the silencing member has ventilation resistance of 1.0 to 4.0kPa·s/m.

It may be preferred that, in the air intake duct of the presentinvention, the silencing member is formed by means of insert-molding tothe duct wall section.

Further, it is to be noted that the above embodiment and preferred modesthereof do not provide all the essential features of the presentinvention, and for example, sub-combination of these modes may alsoconstitute the invention.

Effects of the Invention

According to the air intake duct of the present invention, the duct wallsection formed to the tubular air intake duct is provided with a surfacelayer formed by impregnating thermosetting resin into a porous non-wovenfabric, so that the air intake duct can provide sufficient heatresisting property and water-proof property, as well as more effectivesound reduction function. Further, in a case of only porous non-wovenfabric, good ventilation performance can be achieved with largeradiation noise, and hence, by laminating the ventilation adjustinglayer, the ventilation performance can be properly adjusted with reducedradiation noise.

Furthermore, in the air intake duct according to the present invention,since the silencing member is formed to the duct wall section throughthe insert molding process, it is possible to provide an air intake ducthaving improved intake-air noise attenuation effect without increasingthe number of members or parts. Moreover, it is not necessary toadditionally provide a cover around the outer periphery of the airintake duct, so that the outer diameter of the air intake duct can bereduced, resulting in downsizing of the entire structure of the airintake duct.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] is a schematic view illustrating an air intake passage of aninternal combustion engine.

[FIG. 2] is a perspective view showing the air intake duct according toan embodiment of the present invention.

[FIG. 3] is a perspective view of a halved duct constituting the airintake duct according to the present embodiment.

[FIG. 4] is a sectional view showing a structure of a silencing member.

[FIG. 5] is a graph representing comparison between an Example 1 of anembodiment of the present invention and a Comparative Example 1.

[FIG. 6] is a graph showing comparison between an Example 2 of theembodiment of the present invention and Comparative Examples 1 and 2.

[FIG. 7] is a graph showing comparison between an Example 3 of theembodiment of the present invention and the Comparative Examples 1 and2.

[FIG. 8] is a graph showing comparison between an Example 4 of theembodiment of the present invention and the Comparative Examples 1 and2.

[FIG. 9] is a graph showing measurement of a silenced amount in a widefrequency band area.

MEANS FOR EMBODYING THE INVENTION

Hereunder, a preferred embodiment for carrying out the present inventionwill be explained with reference to the accompanying drawings. Further,it is to be noted that the following embodiment does not limit theinvention defined by appended claims, and all the combination of thesubject features of the present embodiment described herein is notessential for the solution of the present invention.

FIG. 1 is a schematic view illustrating an air intake passage of aninternal combustion engine, FIG. 2 is a perspective view showing the airintake duct according to an embodiment of the present invention, FIG. 3is a perspective view of a halved duct constituting the air intake ductaccording to the present embodiment, and FIG. 4 is a sectional viewshowing a structure of a silencing member.

As shown in FIG. 1, in an air intake passage of an internal combustionengine, a resonator 30 is connected to an air intake duct 10 formed froma duct wall section 11 between an air intake port F and an air cleaner40. The resonator 30 is constructed so as to have a volume calculatedbased on the resonance theory by Helmholtz for reducing noise havingspecific frequency, and a desired intake noise generated in the airintake passage can be reduced by setting a value of such volume to anappropriate value. In addition, for the air intake duct 10 according tothe present embodiment is provided with the duct wall section 11 formedwith a silencing member 20 on the air intake port side F than thelocation of the resonator 30. According to such construction in whichthe duct wall section 11 is formed with the silencing member 20 on theair intake port side F than the location of the resonator 30, the intakenoise can be further effectively reduced. It is to be noted that if theintake noise can be sufficiently reduced only by the location of thesilencing member 20, it is not absolutely necessary to locate theresonator 30.

Next, the air intake duct 10 according to the present embodiment will bedescribed with reference to FIGS. 2 and 3.

As shown in FIG. 2, the air intake duct 10 of the present embodiment isprovided with the duct wall section 11 formed with a resin material inform of tube. Further, since a part of the duct wall section 11 isformed from a grid-shaped frame 12 so as to provide a number of holes 13to the duct wall section 11, and the holes 13 are closed by locating thesilencing member 30 so as to cover such holes 13.

In the air intake duct 10 of the present embodiment, the silencingmember 20 is formed by an insert-molding process, the silencing member20, and the duct wall section 11 and the grid-shaped frame 12 are notbonded together by immersing a synthetic resin material between fibersof the silencing member 20 and then solidifying them. The syntheticresin material is not invaded between the fibers of the silencing member20, and the silencing member 20. The duct wall section 11 and thegrid-shaped frame 12 are mutually joined by an anchor effect of thesurface of the silencing member 20. It is further to be noted that, inthe present embodiment, although an example in which the silencingmember 20 is insert-molded to the duct wall section 11, the silencingmember 20 may be wound up around an outer periphery of the air intakeduct 10 so as to cover the holes 13 of the duct wall section 11.

As shown in FIG. 3, the duct wall section 11 to which the silencingmember 20 is formed by the insert-molding process forms the intake duct10 by halved duct parts 10 a, 10 a by means of butt joining process. Asdescribed above, by forming the duct wall section 11 with the halvedduct parts 10 a, the silencing member 20 can be easily insert-molded tothe duct wall section 11. In addition, as shown in FIG. 2, end portionsof the halved duct parts 10 a in an air flow direction are joined to anengine side duct 14 and an intake side duct 15, respectively, to therebyform one tubular air intake duct 10.

As such joining method, there may be provided general methods utilizedfor resin molding such as vibration welding method, heat plate weldingmethod, ultrasonic welding method and the like, and other than the abovemethods, a bonding method by means of bonding agent, a fastening methodby means of bolt, a fitting method of the respective halved duct parts,and a die slide injection (DSI) method may be also utilized.

Moreover, the number of the holes 13 and area of the holes 13 may bechanged appropriately in consideration of intake noise reducing orattenuating ability of the silencing member 20 to be used. Furthermore,as shown in FIG. 3, since the silencing member 20 is formed through theinsert-molding process so as to be flush in its surface with the innerperipheral surface of the duct wall section 11, the inner peripheralsurface of the duct wall section 11 can be formed to be flat, and hence,fluid passing inside the air intake duct 10 can pass smoothly.

A structure of the silencing member 20 will be described hereunder withreference to FIG. 4.

The silencing member 20 is provided with a surface layer 21 which isformed by impregnating a thermosetting resin to a non-woven fabric and aventilation adjusting layer 22 which is formed of an extendable papermaterial having a rough surface formed in concave/convex shape. Thesurface layer 21 is located to both the outsides of front and back(inner and outer) surfaces of the silencing member 20 so as to interposethe ventilation adjusting layer 22 and an intermediate layer 23therebetween.

The non-woven fabric used for the surface layer 21 has a base materialformed of various fabrics such as aramid fiber, imide fiber,polyvinylchloride fiber, phenol fiber, rayon fiber, polyester fiber,polypropylene fiber, polyamide series fiber, acrylic acid fiber, carbonfiber, glass fiber, alumina fiber (ceramic fiber), boron fiber, novoridefiber, fluorine fiber, metallic fiber or like.

Further, as the thermosetting resin impregnated to the non-woven fabric,there may be used, for example, urethane resin, melamine resin,thermosetting-type acryl resin, thermosetting-type acryl resinparticularly cured by forming ester-link through heating process,urethane resin, epoxy resin, thermosetting-type polyester and the like.

Hereunder, the ventilation adjusting layer 22 will be explained.

The ventilation adjusting layer 22 is formed of an extendable papermaterial as described above.

The extendable paper material may be formed from: a crape-treated paperhaving wrinkled surface shape (wrinkled convex/concave shape); anembossed paper having a surface on which a number of projections areformed, and an embossed-crape-treated paper having a surface on whichwrinkles and a number of projections are formed. On the other hand, as apulp used for the extendable paper material, there may be provided, forexample, hardwood pulp, softwood pulp, hemp pulp, kenaf pulp, bamboopulp, esparto pulp, bagasse pulp, and reedy pulp. Other than naturalpulps such as these wood pulps or non-wood pulps, synthetic resin may bemixed by about 1 to 50% in amount.

The intermediate layer 23 is interposed for adjusting the ventilationresistance of the silencing member 20 in a manner of being sandwichedbetween a pair of ventilation adjusting layers 22. The intermediatelayer 23 is a laminated layer formed of the same substance as that ofthe surface layer 21.

Hereunder, the structure of the silencing member 20 according to thepresent embodiment will be explained.

The silencing member 20 is composed of, as shown in FIG. 4, theintermediate layer 23, a pair of ventilation layers 22 between which theintermediate layer 23 is interposed, and the surface layers 21 which arefurther disposed on the outer surfaces of the ventilation layers 22.Such laminated structure is thereafter subjected to heat-plate fusing bymeans of hot pressing process to thereby provide an integral layerstructure. It is further to be noted that a bonding agent may beinterposed, as occasion demands, between the surface layer 21 and theventilation adjusting layer 22 and between the ventilation adjustinglayer 22 and the intermediate layer 23. As such bonding agent, acrylicresin series bonding agent, urethane resin series bonding agent, epoxyresin series bonding agent, vinyl chloride resin solvent series bondingagent, chloroprene rubber series bonding agent, cyanoacrylate seriesbonding agent, silicone series bonding agent, modified silicone seriesbonding agent, resorcinol series bonding agent and the like may be used.

Further, the silencing member 20 according to the present embodiment isadjusted so as to have a thickness of 1-3 mm after the hot-pressingprocess and ventilation resistance of 1-4 kPa·s/m.

As described above, since the silencing member 20 of the presentembodiment is provided with the intermediate layer 23 formed of the samesubstance as that of the surface layer 21 for adjusting the ventilationresistance, it is possible to prevent manufacturing cost from increasingand to achieve high intake noise attenuation effect.

EXAMPLE

FIGS. 5 to 8 represent results of analyzing the frequencies and thesilenced amounts by the air intake ducts according to the presentembodiment, a conventional air intake duct having silencing functionformed by two tubular pipes are bonded by means of belt-shaped felthaving silencing function (Comparative Example 1) and an air intake ducthaving no silencing function (Comparative Example 2), and the Examplesshown in FIGS. 5 to 8 are adjusted in their ventilation resistances to1.11 kPa·s/m, 1.51 kPa·s/m, 1.63 kPa·s/m, and 1.98 kPa·s/m,respectively.

As represented in FIGS. 5 to 8, in the Examples 1-4, silenced amountequal to or more than that in the Comparative Example 1 in comparisonwith the Comparative Example 2 could be achieved in all the frequencybands (or frequency band ranges). Particularly, as shown in FIG. 5, inthe Example 1, in which the ventilation resistance is adjusted to 1.11kPa·s/m, it is found that particularly large silenced amount wasobtained in comparison with the Comparative Example 1. However, since itis also known that as the silenced amount increases, radiation soundfrom the air intake duct also increases, it may be preferred that theventilation resistance is set to be not less than 1 kPa·s/m.

Furthermore, as shown in FIGS. 5 to 8, it is also found that as theventilation resistance value increases, the value approaches a value ofthe graph of the Comparative Example 1. On the other hand, in a casewhen the ventilation resistance excessively increases, since balancebetween the silenced amount and the radiation sound becomes worse, itmay be preferred that the upper limit of the ventilation resistance isset to about 4 kPa·s/m, more preferably, to about 2 kPa·s/m.

FIG. 9 represents analysis result according to measurement of silencedamount in a wider frequency band range with respect to a conventionalair intake duct (Comparative Example 2) having no silencing function. Inview of the graph of FIG. 9, it is found that the air intake ductaccording to the present embodiment achieves an increased silencedamount in a high frequency band range (4 to 16 kHz). As described above,the air intake duct according to the present invention can also achievehigher silencing function to noise or sound in the high frequency bandrange.

Further, with the air intake duct 10 according to the present invention,although it was explained in the above that the duct wall section 11 isformed from the frame 12 in form of grid to thereby form hole portions13, the duct wall section 11 may be formed from a punched metal platehaving a plurality holes or formed from net-shaped material.

Furthermore, in the forgoing, although it was described that the airintake duct 10 according to the present embodiment is applicable to anintake duct for introducing external air into an internal combustionengine, the air intake duct 10 of the present embodiment is not limitedto such an air intake duct and it may be applied to an air intake ductfor introducing external air for cooling an alternate power supply suchas fuel cell or battery mounted to a vehicle body. In such case, noiseto be absorbed or silenced is a rotating noise or wind noise of a fanfor introducing external air, which is a noise having frequency higherthan that of an intake air noise generated from an internal combustionengine.

Furthermore, in the air intake duct 10 of the present embodimentdescribed above, although the silencing member 20 is applied only to thelinear (straight) portion of the duct wall section 11, the silencingmember 20 may be applied to the curved portion of the air intake duct10. It is thus apparent that such alternation and improved modificationmay be included in the technical scope of the present invention as isapparent from the scope of the appended claims.

REFERENCE NUMERAL

10—air intake duct, 10 a—halved duct parts, 11—duct wall section,12—frame, 13—hole portion, 14—engine side duct, 15—air intake side duct,20—silencing member, 21—surface layer, 22—ventilation adjusting layer,23—intermediate layer, 30—resonator, 40—air cleaner, E—internalcombustion engine, F—air intake port.

1. An air intake duct having a duct wall section formed of resin in formof tube and configured to introduce external air into an internalcombustion engine or alternate power supply system, wherein the ductwall section is provided with a silencing member formed of a laminationof a surface layer formed of a non-woven fabric to which thermosettingresin is impregnated and a ventilation adjusting layer formed of anextendable paper material having a surface in which a plurality ofconcave and convex portions are formed, and the silencing membercomprises at least one pair of the surface layers on front and backsurfaces of at least one pair of the ventilation adjusting layers, andan intermediate layer is formed between the paired ventilation adjustinglayers, the intermediate layer being formed of a same material as thatof the surface layer.
 2. The air intake duct according to claim 1,wherein the intermediate layer is bonded to the ventilation adjustinglayers by means of bonding agent.
 3. The air intake duct according toclaim 1, wherein the silencing member has a thickness of 1.0 to 3.0 mm.4. The air intake duct according to claim 1, wherein the silencingmember has ventilation resistance of 1.0 to 4.0 kPa·s/m.
 5. The airintake duct according to claim 1, wherein the silencing member islocated so as to close the hole portion formed to the duct wall section.6. The air intake duct according to claim 1, wherein the silencingmember is formed by means of insert-molding to the duct wall section.